Engine Trouble Engine Very Low Performance (Torque)

Discussion in '2-Stroke Engines' started by ring2ding, Nov 17, 2014.

  1. ring2ding

    ring2ding New Member

    I just built this bike and I think I'm actually getting it to start, but the torque its outputting is not even enough to keep it running or overpower the internal friction.

    3 principles of combustion:

    1. spark
    ☑ Installed aftermarket 3 prong spark plug (tweaked the gap a little with pliers)
    ☑ Installed new CDI (one that arrived in kit was dead. The spark plug boot plastic fitting was also broken.)
    ☑ ~6V output at external magneto wires
    ☑ Consistent sparking when walking bike at speed
    ☑ Measured a voltage output at spark plug boot (don't remember what it was though)

    2. compression
    ☑ Noticeably harder to walk or pedal when spark plug is installed.
    ? Engine head unscrewed and reinstalled because spark plug didn't fit in frame the way it was originally angled. Is it possible that, now that I've flipped the head around, the combustion isn't happening dead center on the spark plug?
    ? The piston head is pointed upward in the center. Is this expected? (#2 and arrow heading toward exhaust)

    3. fuel
    ☑ Carburetor intake manifold fitting is snug (but I don't think it came with a gasket. Do I need one?)
    - I used a premium fuel blend (switch to regular?)
    - Its pretty cold outside.
    - Located at altitude but using stock carb (not much difference when engine is running between choke on and choke off)
    - Doesn't seem to start well at all without pushing in (fuel flood knob? you know, that button on the carb) a few times. (Is this expected or not?)

    Is there anything I missed? What should I do first, which of these seems most important?
    Last edited: Nov 17, 2014

  2. crassius

    crassius Well-Known Member

    you didn't mention having the choke on - first couple days, it needs choke to start usually

    if you're on 16:1 break-in mix, it will run a bit weakly because of the extra oil

    first tank of fuel is often seen to have a very weak performance since the rings haven't seated yet

    I usually adjust the idle a bit high & just avoid hills untill it starts to run better on 2nd tank
  3. ring2ding

    ring2ding New Member

    Yeah it doesn't start without the choke all the way up. They say that once the bike is running you're supposed to put the choke down, but I can't keep the bike running without actively pedaling it and dropping the choke at that point is hard to do. I managed to do it once but I didn't notice that the engine was running better.

    I am running on the 16:1 break-in mix.

    I really think switching to regular might result in a decent performance boost, but I don't know, and in order to try that I'd have to dump the premium 2 stroke mix into my jeep (which takes regular) and then take off the carb and the fuel line and all that mess and drain it. Do you think its worth it? Am I correct in thinking these bikes should be running regular?

    Also I wonder how worth it it is to buy a better carburetor, especially because I'm at altitude. Do you think this will help a lot too?
    Last edited: Nov 17, 2014
  4. KCvale

    KCvale Motorized Bicycle Vendor

    16:1 is too much oil, I break in with 25:1 non-synthetic for a gallon then go to 32:1 synthetic.

    The stock spark plugs are junk, even the 3 prong ones, get yourself an NGK 5944 (BPR7HIX) Iridium plug, you will feel the difference.

    Note the 7 in the number, the higher the number the more heat the head will dissipate and 7 is ideal for hot places like Phoenix where I am, a 6 will help your engine warm up quicker and run better in cold conditions.

    That should help ya ;-}
  5. crassius

    crassius Well-Known Member

    over time, you should get good at gently moving the choke lever with your right heel while holding a good throttle position with your right hand